Problem: $ { {-1} \times \left[\begin{array}{rr}{2} & {1} \\ {4} & {2} \\ {-2} & {3}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-1}\times{2} & {-1}\times{1} \\ {-1}\times{4} & {-1}\times{2} \\ {-1}\times{-2} & {-1}\times{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-2} & {-1} \\ {-4} & {-2} \\ {2} & {-3}\end{array}\right]}$